The lighting of spaces by a plurality of spaced gas discharge lamps (for example, fluorescent lamps), or incandescent lamps is well known. Commonly, one or more fluorescent lamps are mounted in a fixture with a ballast, and such fixtures are spaced over a ceiling on four foot or eight foot centers. Similarly, overhead fixtures for incandescent lamps may be mounted on centers greater than about two feet. Such lamp fixtures are commonly connected to a single power source and are simultaneously turned on and off or, if provided with dimming capability, are simultaneously dimmed.
It is also known that such overhead fixtures can be individually controlled or dimmed. For example, in a given office space, one worker may prefer or need more or less light intensity than another worker at a spaced work area. Dimming systems are known for selectively dimming the lamps of different fixtures to suit the needs of individual workers. For example, each fixture can be individually hard wired to its own remotely mounted dimmer. However, the installation of this wiring can be quite costly and the determination of which dimmer controls which fixture may not be immediately obvious to the user of the system.
Alternatively the dimmers could be located within each fixture and controlled by signals sent over low voltage wiring or through signals transmitted over the line voltage wiring through a power line carrier system. Unfortunately, both of these approaches require expensive interfaces within each fixture to translate and/or decode the received signals for control of the dimmer.
In another known system, a dimmer with a dimming adjustment control is provided at each fixture, and that control is manually operated, for example by rotating the control with a rigid pole long enough to reach the fixture. In this way, each fixture can be selectively adjusted. However, the system is inconvenient to use and, once the fixture intensity is set, it is difficult or inconvenient to readjust. Moreover, it is difficult to retrofit an existing installation with a control system of this nature.
A known fluorescent controller system is also sold by Colortran Inc. of Burbank, Calif., termed a "sector fluorescent controller" in which an infrared receiver is mounted at a location spaced from its respective fluorescent lamp fixture. Thus, the receiver is fixed to a T-bar, on the wall, on a louver or is counter-sunk flush with wall or ceiling. A ballast controller may be mounted in the lighting fixture, in addition to a conventional dimming ballast. Wiring is then run from the external infrared receiver into the interior of the fixture to the ballast controller. A hand-held remote control infrared transmitter illuminates the infrared receiver at one or more fixtures to control their dimming level.
The need to run wiring from the external sensor complicates the installation of such devices. Further, since the sensor is spaced from the fixture, it requires separate installation, and is visible to view. Moreover, the infrared transmitter of the Colortran device has a transmitting angle of 30.degree.. Therefore, several receivers can be illuminated simultaneously, making selection of control of only one fixture difficult unless the user places himself in a precise location within the room under the fixture to be controlled.
A similar system is sold by the Silvertown Hitech Corporation, where the infrared receiver is mounted to the louvers of a fluorescent fixture. In this system, the infrared receiver is specifically adapted to be mounted to a specific fluorescent fixture.
A further system is sold by Matsushita wherein a single transmitter can be used for independent control of two or more different receivers. This is achieved by adjusting a switch on the transmitter to correspond to a switch setting which has been previously set at the receiver corresponding to the fixture desired to be controlled. For example, fixture A could be controlled when the switch is in position 1 and fixture B could be controlled when the switch is in position 2. In this system, the user must remember which fixture corresponds to which switch position, i.e., A corresponds to 1 and B corresponds to 2.
It is easy for the user to forget and become confused, particularly when there are three or four fixtures controlled by three or four switch positions. This is an undesirable situation. Further, there is a practical limitation on the number of switch positions which can be provided and the number of fixtures in a large room will exceed this. Additionally, there is a great deal of work in programming and reprogramming the receivers for a large number, for example, 20 fixtures.
In comparison, as will be described in more detail later, with the system of the invention, the transmitter is simply pointed at the receiver in the fixture which it is desired to control. This is simple, unambiguous and transparently ergonomic. Further, it does not require any preprogramming or reprogramming of the receivers.
It is also known to use an infrared transmitter for the control of a wall box mounted dimmer, such as the "Grafik Eye" Preset Dimming Control sold by Lutron Electronics Co., Inc., the assignee of the present invention. Also see U.S. Pat. No. 5,191,265 which describes such transmitters. The Grafik Eye Dimmer Control system provides remote control of fixtures and other lamps by a control circuit located at the wall box which controls those fixtures and lamps. An infrared transmitter aimed at the wall box housing produces a beam which contains information to turn on and off and to set the light dimming level of the fixtures being controlled to one of a plurality of preset levels, or to continuously increase or decrease the light level. Other similar systems are sold by Lutron Electronics Co., Inc. under the trademark RanaX-Wireless Dimming Control System. Such systems are not intended to control individual ceiling fixtures in a room independently of other closely spaced fixtures (those fixtures spaced up to about two feet apart).